Before dismissing your current lenses as being inadequate, look at the prices of better lenses. The only unbreakable photographic rule I know of is Good Glass Ain't Cheap. The lenses you have are likely to work just fine when shut down a couple of stops, which means just fine for bright light and flash.

So in terms of price you have to compare the body only Pentax to a two kit lens package for any other brand. And even then you are not getting top grade glass.